CN118251856A

CN118251856A - Pre-decode combiner for Reconfigurable Intelligent Surface (RIS) assisted communications

Info

Publication number: CN118251856A
Application number: CN202180104243.8A
Authority: CN
Inventors: A·埃尔莎菲; A·马诺拉科斯; 张煜; H·D·李; S·莎拉威
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2024-06-25
Also published as: WO2023097489A1

Abstract

Aspects of the present disclosure provide techniques for configuring RIS components to achieve specific goals. According to certain aspects, the first device may: participating in a first training process to obtain a set of channel estimates corresponding to different paths between a second device and the first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components; using the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS components based on at least one target; and communicating with the second device using the RIS components configured according to the combination vector.

Description

Pre-decode combiner for Reconfigurable Intelligent Surface (RIS) assisted communications

Introduction to the invention

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for configuring Reconfigurable Intelligent Surface (RIS) elements.

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcast, or other similar types of services. These wireless communication systems may employ multiple-access techniques capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmission power, or other resources) with the users. The multiple access technique may rely on any of code division, time division, frequency division, orthogonal frequency division, single carrier frequency division, or time division synchronous code division, to name a few examples. These and other multiple access techniques have been adopted in various telecommunications standards to provide a common protocol that enables different wireless devices to communicate at the urban, national, regional, and even global levels.

Despite the tremendous technological advances made over the years in wireless communication systems, challenges remain. For example, complex and dynamic environments may still attenuate or block signals between the wireless transmitter and the wireless receiver, disrupting the various wireless channel measurement and reporting mechanisms established for managing and optimizing the use of limited wireless channel resources. Accordingly, there is a need for further improvements in wireless communication systems to overcome various challenges.

Disclosure of Invention

One aspect provides a method for wireless communication by a first device. The method generally includes: participating in a first training process to obtain a set of channel estimates corresponding to different paths between a second device and the first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components; using the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS components based on at least one target; and communicating with the second device using the RIS components configured according to the combination vector.

One aspect provides a method for wireless communication by a second device. The method generally includes: configuring a first device to participate in a first training process to obtain a set of channel estimates corresponding to different paths between the second device and the first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components; and using the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS components based on at least one target; engaging in the first training process and the second training process with the first device; and communicating with the first device using the RIS components configured according to the combination vector.

Other aspects provide: an apparatus operable to, configured, or otherwise adapted to perform the foregoing methods and those described elsewhere herein; a non-transitory computer-readable medium comprising instructions that, when executed by one or more processors of an apparatus, cause the apparatus to perform the aforementioned methods and those methods described elsewhere herein; a computer program product embodied on a computer-readable storage medium comprising code for performing the foregoing methods and those described elsewhere herein; and an apparatus comprising means for performing the foregoing methods, as well as those methods described elsewhere herein. By way of example, an apparatus may comprise a processing system, a device with a processing system, or a processing system cooperating over one or more networks.

For purposes of illustration, the following description and the annexed drawings set forth certain features.

Drawings

The drawings depict certain features of the aspects described herein and are not intended to limit the scope of the disclosure.

Fig. 1 is a block diagram conceptually illustrating an example wireless communication network.

Fig. 2 is a block diagram conceptually illustrating aspects of an example of a base station and user equipment.

Fig. 3A-3D depict various example aspects of a data structure for a wireless communication network.

Fig. 4A illustrates an example of a communication barrier between wireless communication devices.

Fig. 4B illustrates an example of using RIS to overcome obstructions caused by obstructions between a BS and a UE, in accordance with certain aspects of the present disclosure.

Fig. 5A, 5B, and 5C illustrate examples of training precoding weights for precoding RIS elements in accordance with certain aspects of the present disclosure.

FIG. 6 illustrates an example RIS with sub-RIS components according to certain aspects of the present disclosure.

FIG. 7 illustrates example communications using a RIS with sub-RIS components according to certain aspects of the present disclosure.

Fig. 8A, 8B, 8C, and 8D illustrate examples of training processes in accordance with certain aspects of the present disclosure.

Fig. 9 is a flowchart illustrating example operations for wireless communication by a second device in accordance with aspects of the present disclosure.

Fig. 10 is a flowchart illustrating example operations for wireless communication by a first device in accordance with aspects of the present disclosure.

Fig. 11 depicts aspects of an example communication device.

Fig. 12 depicts aspects of an example communication device.

Detailed Description

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer-readable media for configuring a Reconfigurable Intelligent Surface (RIS) for facilitating communications between wireless devices. For example, a wireless device may include a User Equipment (UE) and a network entity (e.g., a base station such as a gNB) or two UEs (e.g., for side link communications).

RIS typically comprises an array of metamaterials that can interact with radio signals through impedance changes on the tuning surface. For example, the RIS controller can configure and reconfigure at least one RIS element (e.g., a small antenna that reflects radio waves with a configurable time delay or phase shift). According to the present disclosure, when a transmitter transmits a Reference Signal (RS), an RIS controller participates in training between the transmitter and the receiver with the transmitter and the receiver by applying different precoding to RIS elements based on a codebook. The RIS controller receives feedback from the receiver based on the training and applies precoding to the RIS elements based on the feedback and the codebook to enable communication between the transmitter and the receiver.

In general terms, the RIS comprises a plurality of elements that form a surface that can be integrated into different objects such as walls, siding, clothing, etc. The RIS element is a reconfigurable scatterer that includes an antenna that receives and re-radiates (e.g., reflects or refracts) radio wave signals. The RIS elements may be passive, such that no external power is required for re-radiation, and such that re-radiation may be configured with a phase shift for each RIS element. The RIS element may also be active so that the reradiation may change amplitude in addition to phase shift. Thus, the RIS element can perform constructive interference similar to beamforming and re-radiate the beam in certain directions from the transmitter (e.g., UE) toward the receiver (e.g., BS). Such beamforming or precoding of the RIS elements is controlled by identifying each phase shift value or weight to be applied to each RIS element given the specific conditions of the transmitter and receiver.

Aspects of the present disclosure provide techniques for generating precoding weights that can be used in a configured RIS component (e.g., via a RIS controller) to provide efficient or optimized re-radiation. As will be described in more detail below, various RIS components can be designed to be configured in a manner that combines reflected signals to enhance received signals at one UE and/or to cancel reflected signals (zero reflected signals) to reduce interference at one or more other UEs.

Wireless communication network introduction

Fig. 1 depicts an example of a wireless communication system 100 in which aspects described herein may be implemented.

In general, the wireless communication network 100 includes a Base Station (BS) 102, a User Equipment (UE) 104, one or more core networks, such as an Evolved Packet Core (EPC) 160 and a 5G core (5 GC) network 190, that interoperate to provide wireless communication services.

The base station 102 may provide an access point for the user equipment 104 to the EPC 160 and/or 5gc 190 and may perform one or more of the following functions: user data delivery, radio channel encryption and decryption, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio Access Network (RAN) sharing, multimedia Broadcast Multicast Services (MBMS), subscriber and equipment tracking, RAN Information Management (RIM), paging, positioning, delivery of warning messages, and other functions. In various contexts, a base station may include and/or be referred to as a gNB, nodeB, eNB, ng-eNB (e.g., an eNB that has been enhanced to provide connectivity to both EPC 160 and 5gc 190), an access point, a transceiver base station, a radio transceiver, or a transceiver functional unit, or a transmission reception point.

The base station 102 communicates wirelessly with the UE 104 via a communication link 120. Each of the base stations 102 may provide communication coverage for a respective geographic coverage area 110, which may overlap in some cases. For example, a small cell 102 '(e.g., a low power base station) may have a coverage area 110' that overlaps with the coverage area 110 of one or more macro cells (e.g., high power base stations).

The communication link 120 between the base station 102 and the UE 104 may include Uplink (UL) (also known as reverse link) transmissions from the user equipment 104 to the base station 102 and/or Downlink (DL) (also known as forward link) transmissions from the base station 102 to the user equipment 104. In aspects, communication link 120 may use multiple-input multiple-output (MIMO) antenna techniques including spatial multiplexing, beamforming, and/or transmit diversity.

Examples of UEs 104 include a cellular phone, a smart phone, a Session Initiation Protocol (SIP) phone, a laptop, a Personal Digital Assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player, a camera, a game console, a tablet device, a smart device, a wearable device, a vehicle, an electricity meter, an air pump, a large or small kitchen appliance, a healthcare device, an implant, a sensor/actuator, a display, or other similar devices. Some of the UEs 104 may be internet of things (IoT) devices (e.g., parking meters, air pumps, ovens, vehicles, heart monitors, or other IoT devices), always-on (AON) devices, or edge processing devices. The UE 104 may also be more generally referred to as a station, mobile station, subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, or client.

Communications using higher frequency bands may have higher path loss and shorter distances than lower frequency communications. Thus, some base stations (e.g., 180 in fig. 1) may utilize beamforming 182 with the UE 104 to improve path loss and distance. For example, the base station 180 and the UE 104 may each include multiple antennas, such as antenna elements, antenna panels, and/or antenna arrays, to facilitate beamforming.

In some cases, the base station 180 may transmit the beamformed signals to the UE 104 in one or more transmission directions 182'. The UE 104 may receive the beamformed signals from the base station 180 in one or more receive directions 182 ". The UE 104 may also transmit the beamformed signals to the base station 180 in one or more transmission directions 182 ". The base station 180 may also receive beamformed signals from the UEs 104 in one or more receive directions 182'. The base station 180 and the UE 104 may then perform beam training to determine the best receive direction and transmit direction for each of the base station 180 and the UE 104. It is noted that the transmission direction and the reception direction of the base station 180 may be the same or different. Similarly, the transmit direction and the receive direction of the UE 104 may be the same or different.

Wireless communication network 100 includes an RIS component 199 that can be configured to participate in training of RIS elements. Wireless network 100 also includes an RIS component 198 that can be configured to participate in training of RIS elements.

Fig. 2 depicts aspects of an example Base Station (BS) 102 and User Equipment (UE) 104.

In general, base station 102 includes various processors (e.g., 220, 230, 238, and 240), antennas 234a through 234t (collectively 234), transceivers 232a through 232t (collectively 232) including modulators and demodulators, and other aspects that enable wireless transmission of data (e.g., data source 212) and wireless reception of data (e.g., data sink 239). For example, the base station 102 may send and receive data between itself and the user equipment 104.

The base station 102 includes a controller/processor 240 that may be configured to implement various functions related to wireless communications. In the depicted example, controller/processor 240 includes RIS component 241, which may represent PHR component 199 of FIG. 1. Notably, while depicted as an aspect of controller/processor 240, in other implementations RIS component 241 can additionally or alternatively be implemented in various other aspects of base station 102.

In general, the user equipment 104 includes various processors (e.g., 258, 264, 266, and 280), antennas 252a-r (collectively 252), transceivers 254a-r (collectively 254) including modulators and demodulators, and other aspects that enable wireless transmission of data (e.g., data source 262) and wireless reception of data (e.g., data sink 260).

The user equipment 104 includes a controller/processor 280 that may be configured to implement various functions related to wireless communications. In the depicted example, controller/processor 280 includes RIS component 281, which may represent RIS component 198 of FIG. 1. Notably, while depicted as an aspect of the controller/processor 280, in other implementations, the RIS component 281 can additionally or alternatively be implemented in various other aspects of the user equipment 104.

Fig. 3A-3D depict aspects of a data structure for a wireless communication network, such as wireless communication network 100 of fig. 1. Specifically, fig. 3A is a diagram 300 illustrating an example of a first subframe within a 5G (e.g., 5G NR) frame structure, fig. 3B is a diagram 330 illustrating an example of a DL channel within a 5G subframe, fig. 3C is a diagram 350 illustrating an example of a second subframe within a 5G frame structure, and fig. 3D is a diagram 380 illustrating an example of a UL channel within a 5G subframe.

Further discussion regarding fig. 1,2, and 3A-3D is provided later in this disclosure.

MmWave wireless communication profile

In wireless communications, the electromagnetic spectrum is typically subdivided into various categories, bands, channels, or other features. Subdivision is typically provided based on wavelength and frequency, where frequency may also be referred to as a carrier, subcarrier, channel, tone, or subband.

A 5G network may utilize several frequency ranges, which in some cases are defined by standards such as the 3GPP standard. For example, while 3GPP technical standard TS 38.101 currently defines frequency range 1 (FR 1) as including 600MHz-6GHz, certain uplink and downlink allocations may fall outside of this general range. Accordingly, FR1 is commonly referred to as the (interchangeably) "sub-6 GHz" band.

Similarly, although TS 38.101 presently defines frequency range 2 (FR 2) as including 26GHz-41GHz, again, the particular uplink and downlink allocations may fall outside of this general range. FR2 is sometimes referred to as the (interchangeably) "millimeter wave" or "mmWave" band, although it differs from the Extremely High Frequency (EHF) band (30 GHz-300 GHz) identified by the International Telecommunications Union (ITU) as the "millimeter wave" band, because the wavelengths at these frequencies are between 1 millimeter and 10 millimeters.

Communications using the mmWave/near mmWave radio frequency band (e.g., 3GHz-300 GHz) may have higher path loss and shorter distances than lower frequency communications. As described above with respect to fig. 1, a base station (e.g., 180) configured to communicate using mmWave/near mmWave radio frequency bands may utilize beamforming (e.g., 182) with a UE (e.g., 104) to improve path loss and distance.

Example application and precoding of Reconfigurable Intelligent Surfaces (RIS)

Large-scale multiple-input multiple-output (MIMO) configurations increase throughput. For example, MIMO may achieve high beamforming gain by using Active Antenna Units (AAUs) and may operate with separate Radio Frequency (RF) chains for each antenna port. Unfortunately, the use of AAUs can significantly increase power consumption.

To further take advantage of this and extend coverage, RIS can be deployed to reflect impinging waves in the desired direction. In some cases, RIS can operate without significant power consumption when the RIS passively operates to reflect or refract beams only from the transmitter to the receiver. In some cases, the reflection or refraction direction may be controlled by the gNB or the monitoring side link UE.

Fig. 4A illustrates an example of a communication obstruction between wireless communication devices. As shown, due to the blocking obstruction, the first network entity (gNB) can only transmit to the first UE (UE 1) but cannot reach the second UE (UE 2) because the blocker prevents the signal from reaching UE2. The barrier also prevents UE1 from establishing side-link communication with UE2. As such, UE2 may not be able to communicate with the gNB or UE 1.

FIG. 4B illustrates an example of using a RIS to overcome a barrier in accordance with certain aspects of the present disclosure. As shown, the RIS may be introduced to reflect or otherwise re-radiate the radio signal so that it bypasses the barrier. For example, communication between the gNB and the UE2 may be achieved by the RIS re-radiating one or more beams from the gNB towards the UE2 or vice versa. In addition, the RIS may also be reconfigured (i.e., direct incoming and outgoing beams at different angles) to enable UE1 and UE2 to establish side link communications.

The RIS may perform passive beamforming. For example, the RIS may receive signal power from a transmitter (e.g., gNB, UE1, and/or UE 2) that is proportional to the number of RIS elements thereon. When the RIS reflects or refracts the radio signal, the RIS element causes a phase shift to perform conventional beamforming or precoding. The phase shift is controlled by pre-coding weights (e.g., multipliers or time delayed offsets) applied to the RIS elements. For example, for an array of RIS elements, such as an m n rectangular matrix, the RIS controller may generate or assign a respective precoding weight for each of the RIS elements.

Training for RIS 510 may be performed using a series of Time Division Multiplexed (TDM) reference signals (RS 1-RSK) as shown in FIG. 5A. The training RS may be, for example, SSB, CSI-RS, or Tracking Reference Signal (TRS). The RIS may be configured (e.g., via a RIS controller) to use a different Beamforming (BF) codebook for each RS occasion/transmission. In some cases, training may be performed to determine a common phase/coefficient α used across RIS elements (or elements of a sub-RIS). If multiple RISs or sub-RISs are used, the training process may be repeated for different RISs or sub-RISs. The weights and/or beams for each RIS may be designed using a variety of techniques. In some cases, such training may produce a combined vector that includes a set of common coefficients (weights/beams), where the common coefficients from the set are used at each RIS component.

In the example shown in fig. 5B, the UE repeatedly transmits the RS sequence with different beams, while the gNB measures a received signal metric, such as spectral efficiency or signal-to-interference-and-noise ratio (SINR). As shown in fig. 5C, the winning beam may be declared as the beam corresponding to the highest received signal metric (520). The gNB may evaluate the different receive beams as part of training such that the end result is also to select a transmit/receive beam pair (e.g., the transmit beam of the UE and the receive beam of the gNB). Similar training may be performed with the gNB as a transmitter and the UE as a receiver.

As shown in FIG. 6, in some cases, elements of a RIS may be divided into groups (or clusters) called sub-RISs. Each sub-RIS may be considered a separate RIS with its own weights for pre-decoding its RIS elements. Such cluster-based weight generation may reduce overall computational effort when there are a large number of RIS elements. For example, the RIS controller can generate a weight (digital fourier transform or DFT) vector for each small cluster, subset, or portion of RIS elements, such as size M ₁×N₁. The RIS controller can then apply the same DFT vectors generated for that subset across other subsets. The RIS controller can generate varying DFT vectors for the remaining RIS elements according to a pattern, such as by shifting or scaling the DFT vectors generated for the initial subset. The RIS controller may also generate different DFT vectors if desired.

The example RIS shown in fig. 6 has three subsets or sub-RIS: child RIS (1), (2) and (3). The RIS controller may use any suitable technique to generate a codebook for the child RIS (1). In some cases, the sub-RIS (2) and the sub-RIS (3) may use the same codebook generated for sub-RIS (1). In some cases, the combining vector may be based on a PMI codebook. In such cases, the codebook may be configured by a first device (e.g., a gNB or UE). In some cases, the codebook may be configured based at least in part on feedback recommendations from a second device (e.g., a gNB or UE involved in training with a first device).

In some cases, a single index may be used as a starting DFT index that causes other clusters to have shifted versions of the index. That is, the DFT weights may be associated with the starting index for generating one or more shifted versions of the DFT weights. One or more shifted versions of the DFT weights may be applied to other subsets of RIS elements. For example, if index 4 is used in sub RIS (1), index 5 may be used in sub RIS (2), index 6 may be used in sub RIS (3), and so on. In some cases, it may also be possible to repeat the same index across different sub-RISs or clusters. In aspects, the all-zero vector (if generated) is still part of the codebook, such that the RIS controller can disable one or more of the sub-RIS.

Example combiner for RIS assisted communications

Aspects of the present disclosure provide techniques for configuring RIS components to achieve specific goals. For example, the RIS component may be configured to combine the reflected signals to enhance the received signal at one UE. Alternatively, or in addition, the reflected signal may be cancelled (nulled) to reduce interference at one or more other UEs.

Fig. 7 shows how RIS components in the system may cause multiple reflected signals at the UE. The illustrated example shows different paths from the gNB (gNB 1) to the UE via a first RIS (RIS 1 (with 3 clusters: sub-RIS 1, sub-RIS 2 and sub-RIS 3)), a second RIS (RIS 2) and a third RIS (RIS 3).

Let h _i denote an equivalent channel vector of size N _T x1, where N _T is the gNB transmit antenna at Resource Element (RE) k (or a set of REs within a coherent BW). In the example shown, h ₀ represents the equivalent channel directly from gNB1 to the UE. h ₁₁ represents the equivalent channel reflected from gNB1, from sub-RIS 1 to the UE, h ₁₂ represents the equivalent channel reflected from gNB1, from sub-RIS 2 to the UE, and h ₁₃ represents the equivalent channel reflected from gNB1, from sub-RIS 3 to the UE. h ₂ represents the equivalent channel reflected from gNB1, from RIS2 to the UE, and h ₃ represents the equivalent channel reflected from gNB1, from RIS 3.

The effect of RIS on the channel can be expressed in the corresponding equivalent channel formula. For example, for sub RIS1, channel (denoted as an array of channel coefficients) h11 can be expressed as:

h11＝G11×Phi11×H11，

where H11 has a size (number of elements in child RIS1 plus number of N_Tx); phi11 is a diagonal matrix having a size (the number of elements in sub RIS 1x the number of elements in sub RIS 1); and G11 has a size (number of n_rx×the number of elements in the sub RIS 1). G11 may be assumed to include filtering at the UE.

Assuming α _ij is a common weight (phase/coefficient) vector used across all elements of the j-th sub-RIS/cluster of the i-th RIS, the received signal at the UE can be expressed as:

α₀h₀+α₁₁h₁₁+α₁₂h₁₂+α₁₃h₁₃+α₂h₂+α₃h₃.

If the number of RIS reflections is equal to the size of the channel vector (N _T), then the UE (or more generally, the reference signal receiver; gNB in UL and UE in DL or SL) may be able to control the signal to zero or combine or implement various combinations, which may be expressed as:

Wherein H has a number of sizes N _T x RIS (sub RIS).

A _α (a combination vector of coefficients used to configure the RIS component) can be designed to achieve various goals. For example, a _α may be designed to use Singular Value Decomposition (SVD) to obtain the optimal signal combination (or zero forcing) by selecting the eigenvector corresponding to the highest eigenvalue. In such cases, the eigenvectors (column/pre-decoder/beamformer) may be obtained based on SVD for H.

If the number of RIS reflections [ child RIS ] is greater than N _T, A _α may be designed to zero (or a null space may be calculated) the interference at the UE, for example, by using SVD and selecting a eigenvector corresponding to a zero eigenvalue. In such cases, zero forcing may be based on the following formula:

This may be solved using any suitable method or using eigenvectors corresponding to zero eigenvalues (or very small eigenvalues, e.g., below a threshold value) of matrix H. Based on this, the UE may perform SVD or eigenvalue decomposition on H. If SVD is performed based on the best eigenvalue/vector (e.g., to maximize performance such as SINR/rate/throughput), the UE may select a non-zero eigenvector corresponding to the non-zero eigenvalue (e.g., the best SVD pre-decoder may be considered as the non-zero eigenvector corresponding to the largest eigenvalue of matrix H). If zero forcing is performed, the UE may apply SVD to H, then select the eigenvector corresponding to zero (or may select a very small eigenvalue based on a threshold), and may use one of those vectors.

The appropriate combination vector a _α for such targets may be determined by performing a training process involving the RIS element. For example, fig. 8A-8D show examples of how such training may be performed with the child RIS (child RIS1, child RIS2, and child RIS 3) of the RIS.

The first part of the training may involve training each sub-RIS individually to obtain a corresponding PHI (diagonal matrix). The gNB may transmit 4 Time Division Multiplexed (TDM) reference signals associated with the same spatial beam (e.g., a single SSB/TRS).

As shown in fig. 8A, the gNB transmits the first RS (RS 1) directly to the UE, wherein all sub-RSs are turned off, allowing the UE to measure h ₀. As shown in fig. 8B, the gNB transmits a second RS (i.e., RS 2), where only the sub RIS1 is turned on, allowing the UE to measure h ₁₁. As shown in fig. 8C, the gNB transmits a third RS (RS 2), with the child RIS2 turned on, allowing the UE to measure h ₁₂. As shown in fig. 8D, the gNB transmits a fourth RS (RS 2), with the child RIS3 turned on, allowing the UE to measure h ₁₃. In some cases, the UE may report information about these measurements. When all sub-RIS are on, the signal received by the UE can be expressed as:

Based on these measurements, the gNB may request the UE to calculate a _α. Alternatively, the gNB may configure a certain number (e.g., X) of PMIs (e.g., zero forcing and combiner of different PMIs for different purposes). In such cases, the UE may try those PMIs and then decide which PMI is best suited: 1) combiner/SVD; or 2) ZF.

In some cases, a _α may be generated by a receiver (e.g., a UE or a gNB receiving the RS), which may calculate, quantize, and send it to all controllers and gnbs. In some cases, a _α may be based on a codebook/PMI defined by the gNB and RIS controller to handle common weights across all elements (which may be specified in terms of each RIS). If the RIS has a particular capability of refinement coefficients/weights α _ij, then the scenario may be taken into account when calculating A _α.

In some cases, the UE may signal PMI or a _α to the gNB. In such cases, the gNB may communicate with a controller of the RIS). In some cases, the UE may signal PMI or a _α to the controller of the RIS. In such cases, the controller of each RIS may use a common phase α _i across all elements.

As noted above, if a surface of a RIS has many elements, the surface may be partitioned into multiple sub-RISs. In such cases, the RIS controller may divide the surface of the RIS into L clusters/sub RIS, where L > = n_tx, where n_tx is the number of antennas (or antenna ports) at the TX side (gNB or UE).

One benefit of such clustering or use of sub-RIS is that each sub-RIS beamformer/configuration can be well trained. In such cases, the common coefficients may then be obtained by the receiver based on BF or ZF. This may also help reduce the time-switching (and processing overhead) to change all coefficients, as each sub-RIS is smaller in size and beam optimization should be simpler.

In some cases, the gNB may configure the UE to calculate the PMI based on the desired object (a _α). For example, the UE may calculate PMI based on SVD (e.g., to obtain an optimal combiner), based on ZF (zero space) (to achieve interference cancellation), or both. In some cases, the UE may be configured to calculate the PMI based on SVD, ZF, or both according to Radio Resource Control (RRC), medium Access Control (MAC) Control Element (CE), or Downlink Control Information (DCI). Additionally, or alternatively, the UE may be configured via a dedicated Physical Downlink Shared Channel (PDSCH), side link control information (SCI), or a dedicated physical side link shared channel (PSSCH). In this context, dedicated may refer to PDSCH/PSSCH transmissions sent for this purpose.

In some cases, a _α may be designed based on the instantaneous channel (such as worst case or best case channel covariance matrix—based on eigenvalues). In other cases, a _α may be designed based on the average covariance matrix across all REs.

Example method

Fig. 9 is a flowchart illustrating example operations 900 for wireless communication by a second device in accordance with certain aspects of the present disclosure. The operations 900 may be performed, for example, by a network entity (e.g., such as BS102 shown in fig. 1 and 2) or by a UE (e.g., such as UE 104 shown in fig. 1 and 2). The operations 900 may be implemented as software components executing and running on one or more processors (e.g., the controller/processor 240 of fig. 2). Further, the signal transmission and reception by the BS in operation 900 may be implemented by one or more antennas (e.g., antenna 234 of fig. 2), for example. In certain aspects, signal transmission and/or reception by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor 240) that obtains and/or outputs signals.

The operation 900 may begin at a first block 910 by: the first device is configured to participate in a first training process to obtain a set of channel estimates corresponding to different paths between the second device and the first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components, and the second training process is participated in using the set of channel estimates to obtain a combined vector of coefficients for configuring the RIS components based on at least one target. At 920, the second device participates in the first training process and the second training process with the first device. At 930, the second device communicates with the first device using the RIS component configured according to the combined vector.

Fig. 10 is a flowchart illustrating example operations 1000 for wireless communication by a first device in accordance with certain aspects of the present disclosure. The operations 1000 may be performed, for example, by a UE (e.g., such as the UE 104 shown in fig. 1 and 2) or a base station (such as the base station 102 shown in fig. 1 and 2). The operations 1000 may be implemented as software components executing and running on one or more processors (e.g., the controller/processor 280 of fig. 2). Further, the signal transmission and reception by the BS in operation 1000 may be implemented by one or more antennas (e.g., antenna 252 of fig. 2), for example. In certain aspects, transmission and/or reception of signals by the BS may be implemented via a bus interface that obtains and/or outputs signals by one or more processors (e.g., controller/processor 280).

Operation 1000 begins at 1010 by: a first training process is engaged to obtain a set of channel estimates corresponding to different paths between a second device and a first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components. At 1020, the first device uses the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS component based on the at least one target. At 1030, the first device communicates with the second device using the RIS component configured according to the combined vector.

Example Wireless communication device

Fig. 11 depicts an example communication device 1100 that includes various components capable of operating, configured, or adapted to perform operations for the techniques disclosed herein, such as the operations depicted and described with respect to fig. 9. In some examples, the communication device 1100 may be a base station 102 or a UE 104 as described, for example, with respect to fig. 1 and 2.

The communication device 1100 includes a processing system 1102 coupled to a transceiver 1108 (e.g., a transmitter and/or receiver). Transceiver 1108 is configured to transmit (or send) and receive signals for communication device 1100, such as the various signals described herein, via antenna 1110. The processing system 1102 may be configured to perform processing functions for the communication device 1100, including processing signals received by and/or to be transmitted by the communication device 1100.

The processing system 1102 includes one or more processors 1120 coupled to a computer-readable medium/memory 1130 via a bus 1106. In certain aspects, the computer-readable medium/memory 1130 is configured to store instructions (e.g., computer-executable code) that, when executed by the one or more processors 1120, cause the one or more processors 1120 to perform the operations shown in fig. 9 or other operations for performing various techniques discussed herein for participating in training of RIS elements.

In the depicted example, computer-readable medium/memory 1130 stores code 1131 for configuring a first device to participate in a first training process to obtain a set of channel estimates corresponding to different paths between a second device and the first device that involve reflections from different Reconfigurable Intelligent Surface (RIS) components, and using the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS components based on at least one target; code 1132 for participating in a first training process and a second training process with the first device; code 1133 for communicating with the first device using the RIS component configured according to the combined vector.

In the depicted example, the one or more processors 1120 include circuitry configured to implement code stored in the computer-readable medium/memory 1130, the circuitry including circuitry 1121 to configure a first device to participate in a first training process to obtain a set of channel estimates corresponding to different paths between a second device and the first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components, and to use the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS components based on at least one target; circuitry 1122 to participate in a first training process and a second training process with the first device; to communicate with circuitry 1124 of the RIS component configured according to the combination vector to communicate with the first device.

The various components of the communication device 1100 may provide means for performing the methods described herein, including with respect to fig. 9.

In some examples, the means for transmitting or sending (or the means for outputting for transmission) may include the transceiver 232 and/or the antenna 234 of the base station 102 shown in fig. 2 and/or the transceiver 1108 and the antenna 1110 of the communication device 1100 in fig. 11.

In some examples, the means for receiving (or means for obtaining) may include the transceiver 232 and/or the antenna 234 of the base station shown in fig. 2 and/or the transceiver 1108 and the antenna 1110 of the communication device 1100 in fig. 11.

In some cases, a device may not actually transmit, for example, signals and/or data, but may have an interface (means for outputting) for outputting signals and/or data for transmission. For example, the processor may output signals and/or data to a Radio Frequency (RF) front end via a bus interface for transmission. Similarly, a device may not actually receive signals and/or data, but may have an interface (means for obtaining) for obtaining signals and/or data received from another device. For example, the processor may obtain (or receive) signals and/or data from the RF front end via the bus interface for reception. In various aspects, the RF front-end may include various components including transmit and receive processors, transmit and receive MIMO processors, modulators, demodulators, and the like, such as depicted in the example of fig. 2.

In some examples, the means for receiving and/or obtaining may include various processing system components, such as: one or more processors 1120 in fig. 11, or aspects of base station 102 depicted in fig. 2, include a receive processor 238, a transmit processor 220, a TX MIMO processor 230, and/or a controller/processor 240 (including a CSI component 241).

It is noted that fig. 11 is an example, and that many other examples and configurations of communication device 1100 are possible.

Fig. 12 depicts an example communication device 1200 that includes various components capable of operating, configured, or adapted to perform operations for the techniques disclosed herein, such as the operations depicted and described with respect to fig. 10. In some examples, the communication device 1000 may be a user equipment 104 as described, for example, with respect to fig. 1 and 2.

The communication device 1200 includes a processing system 1202 coupled to a transceiver 1208 (e.g., transmitter and/or receiver). The transceiver 1208 is configured to transmit (or send) and receive signals for the communication device 1200, such as the various signals described herein, via the antenna 1210. The processing system 1202 may be configured to perform processing functions for the communication device 1200, including processing signals received by the communication device 1200 and/or to be transmitted by the communication device.

The processing system 1202 includes one or more processors 1220 coupled to a computer-readable medium/memory 1230 via bus 1206. In certain aspects, the computer-readable medium/memory 1230 is configured to store instructions (e.g., computer-executable code) that, when executed by the one or more processors 1220, cause the one or more processors 1220 to perform the operations shown in fig. 10 or other operations for performing the various techniques discussed herein for participating in training of RIS elements.

In the depicted example, computer-readable medium/memory 1230 stores: code 1231 for participating in a first training process to obtain a set of channel estimates corresponding to different paths between a second device and a first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components; code 1232 for using the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS component based on at least one target; and code 1233 for communicating with the second device using the RIS component configured according to the combined vector.

In the depicted example, the one or more processors 1220 include circuitry configured to implement code stored in the computer-readable medium/memory 1230, the circuitry comprising: circuitry 1221 for participating in a first training process to obtain a set of channel estimates corresponding to different paths between a second device and a first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components; circuitry 1222 for using the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS component based on at least one target; and circuitry 1224 for communicating with the second device using the RIS component configured according to the combined vector.

The various components of the communication device 1200 may provide means for performing the methods described herein, including with respect to fig. 9.

In some examples, the means for transmitting or sending (or means for outputting for transmission) may include the transceiver 254 and/or antenna 252 of the user equipment 104 shown in fig. 2 and/or the transceiver 1208 and antenna 1210 of the communication device 1200 in fig. 12.

In some examples, the means for receiving (or means for obtaining) may include the transceiver 254 and/or the antenna 252 of the user equipment 104 shown in fig. 2 and/or the transceiver 1208 and the antenna 1210 of the communication device 1200 in fig. 12.

In some examples, the means for generating and/or the means for transmitting may include various processing system components, such as: one or more processors 1220 in fig. 12, or aspects of user equipment 104 depicted in fig. 2, include a receive processor 258, a transmit processor 264, a TX MIMO processor 266, and/or a controller/processor 280 (including a CSI management component 281).

It is noted that fig. 12 is an example, and that many other examples and configurations of communication device 1200 are possible.

Example clauses

Specific examples of implementations are described in the following numbered clauses:

Clause 1: a method for wireless communication by a first device, comprising: participating in a first training process to obtain a set of channel estimates corresponding to different paths between a second device and the first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components; using the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS component based on at least one target; and communicating with the second device using the RIS component configured according to the combination vector.

Clause 2: the method of clause 1, wherein: the first device comprises a User Equipment (UE) and the second device comprises a base station; the first device comprises a base station and the second device comprises a UE; or the first device comprises a UE and the second device comprises a UE.

Clause 3: the method of any one of clauses 1-2, wherein the at least one object is to combine signals reflected by the RIS component to enhance the received signal at the first device.

Clause 4: the method of clause 3, wherein the combined vector is obtained using singular value decomposition to select the eigenvector corresponding to the highest eigenvalue.

Clause 5: the method of any one of clauses 1 to 4, wherein the at least one objective is to cancel a signal reflected by the RIS component to zero interference at one or more other devices.

Clause 6: the method of clause 5, wherein the combined vector is obtained using singular value decomposition to select a eigenvector corresponding to a zero eigenvalue.

Clause 7: the method of any one of clauses 1 to 6, wherein the combination vector comprises a set of common coefficients, wherein the common coefficients from the set are used at each RIS component.

Clause 8: the method of clause 7, wherein the RIS component comprises one or more individual RIS and one or more RIS clusters.

Clause 9: the method of clause 8, wherein the set of common coefficients comprises common coefficients used across all elements of different RIS in the RIS cluster.

Clause 10: the method of any of clauses 1-9, wherein participating in the first training process comprises: performing a first channel measurement based on a first reference signal received when all of the RIS components are disabled; and performing one or more other channel measurements based on the one or more reference signals received when only one RIS component is enabled.

Clause 11: the method of clause 10, wherein the first device calculates the combining vector based on a first channel measurement and other channel measurements.

Clause 12: the method of any one of clauses 1 to 11, wherein the first device calculates the combined vector, quantizes the value of the combined vector, and transmits the quantized value to at least one of a RIS controller or the second device.

Clause 13: the method of any one of clauses 1 to 12, wherein: the combining vector is based on a Precoding Matrix Indicator (PMI) codebook; and the codebook is configured by the first device or the codebook is configured based at least in part on feedback recommendations from the second device.

Clause 14: the method of any one of clauses 1 to 13, wherein the RIS component comprises a portion of the RIS surface segmented into sub-RIS.

Clause 15: the method of any one of clauses 1 to 14, further comprising: signaling is received indicating the at least one target on which the combining vector is based.

Clause 16: the method of clause 15, wherein the signaling comprises at least one of Radio Resource Control (RRC), medium Access Control (MAC) Control Element (CE), or Downlink Control Information (DCI) signaling a Physical Downlink Shared Channel (PDSCH), side link control information (SCI), or physical side link shared channel (PSSCH).

Clause 17: a method for wireless communication by a second device, comprising: configuring a first device to participate in a first training process to obtain a set of channel estimates corresponding to different paths between a second device and the first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components, and using the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS components based on at least one target; engaging in the first training process and the second training process with the first device; and communicating with the first device using the RIS component configured according to the combination vector.

Clause 18: the method of clause 17, wherein the participating comprises: receiving information about the combined vector of coefficients from the first device; and communicating with one or more RIS controllers to configure the RIS component according to the information.

Clause 19: the method of any of clauses 17 to 18, wherein the engaging comprises requiring the first device to calculate the combined vector.

Clause 20: the method of any one of clauses 17-19, wherein the second device configures a plurality of Precoding Matrix Indicators (PMIs), and receives an indication of one of the plurality of PMIs from the first device.

Clause 21: an apparatus, comprising: at least one processor; and a processor coupled with the at least one memory, wherein the memory includes instructions executable by the at least one processor to cause the apparatus to perform the method according to any one of clauses 1-20.

Clause 22: an apparatus comprising means for performing the method of any one of clauses 1 to 20.

Clause 23: a non-transitory computer-readable medium comprising: executable instructions that, when executed by one or more processors of an apparatus, cause the apparatus to perform the method according to any one of clauses 1 to 20.

Additional wireless communication network considerations

The techniques and methods described herein may be used for various wireless communication networks (or Wireless Wide Area Networks (WWANs)) and Radio Access Technologies (RATs). Although aspects may be described herein using terms commonly associated with 3G, 4G, and/or 5G (e.g., 5G New Radio (NR)) wireless technologies, aspects of the present disclosure may be equally applicable to other communication systems and standards not explicitly mentioned herein.

The 5G wireless communication network may support various advanced wireless communication services, such as enhanced mobile broadband (eMBB), millimeter wave (mmWave), machine Type Communication (MTC), and/or ultra-reliable, low latency communication for mission critical (URLLC). These services and other services may include latency and reliability requirements.

Returning to fig. 1, aspects of the present disclosure may be performed within an example wireless communication network 100.

In 3GPP, the term "cell" can refer to a coverage area of a node B and/or a narrowband subsystem serving the coverage area, depending on the context in which the term is used. In an NR system, the terms "cell" and BS, next generation NodeB (gNB or gNodeB), access Point (AP), distributed Unit (DU), carrier wave, or transmission reception point may be used interchangeably. The BS may provide communication coverage for macro cells, pico cells, femto cells, and/or other types of cells.

A macro cell may generally cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. The pico cell may cover a relatively small geographic area (e.g., a gym) and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., home) and may allow restricted access by UEs associated with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG) and UEs of users in the home). The BS for the macro cell may be referred to as a macro BS. The BS for the pico cell may be referred to as a pico BS. The BS for the femto cell may be referred to as a femto BS, a home BS, or a home NodeB.

A base station 102 configured for 4G LTE, collectively referred to as an evolved Universal Mobile Telecommunications System (UMTS) terrestrial radio access network (E-UTRAN), may interface with the EPC 160 through a first backhaul link 132 (e.g., an S1 interface). A base station 102 configured for 5G (e.g., 5G NR or next generation RAN (NG-RAN)) may interface with the 5gc 190 over the second backhaul link 184. The base stations 102 may communicate with each other directly or indirectly (e.g., through EPC 160 or 5gc 190) over a third backhaul link 134 (e.g., an X2 interface). The third backhaul link 134 may be generally wired or wireless.

The small cell 102' may operate in licensed and/or unlicensed spectrum. When operating in unlicensed spectrum, the small cell 102' may employ NR and use the same 5GHz unlicensed spectrum as used by the Wi-Fi AP 150. The use of small cells 102' of NR in the unlicensed spectrum may improve coverage of the access network and/or increase capacity of the access network.

Some base stations, such as the gNB 180, may operate in the traditional sub-6 GHz spectrum, millimeter wave (mmWave) frequencies, and/or frequencies near mmWave to communicate with the UE 104. When the gNB 180 operates in mmWave or frequencies near mmWave, the gNB 180 may be referred to as a mmWave base station.

The communication link 120 between the base station 102 and, for example, the UE 104 may be over one or more carriers. For example, for each carrier allocated in carrier aggregation up to yxmhz (x component carriers) in total for transmission in each direction, base station 102 and UE 104 may use a spectrum up to Y MHz (e.g., 5MHz, 10MHz, 15MHz, 20MHz, 100MHz, 400MHz, and other MHz) bandwidth. The carriers may or may not be adjacent to each other. The allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL than UL). The component carriers may include a primary component carrier and one or more secondary component carriers. The primary component carrier may be referred to as a primary cell (PCell) and the secondary component carrier may be referred to as a secondary cell (SCell).

The wireless communication system 100 further includes a Wi-Fi Access Point (AP) 150 that communicates with Wi-Fi Stations (STAs) 152 via a communication link 154 in, for example, the 2.4GHz and/or 5GHz unlicensed spectrum. When communicating in the unlicensed spectrum, STA 152/AP 150 may perform Clear Channel Assessment (CCA) prior to communication to determine whether a channel is available.

Some UEs 104 may communicate with each other using a device-to-device (D2D) communication link 158. The D2D communication link 158 may use the DL/UL WWAN spectrum. The D2D communication link 158 may use one or more side link channels, such as a physical side link broadcast channel (PSBCH), a physical side link discovery channel (PSDCH), a physical side link shared channel (PSSCH), and a physical side link control channel (PSCCH). D2D communication may be through a variety of wireless D2D communication systems such as, for example, FLASHLINQ, WIMEDIA, bluetooth, zigBee, wi-Fi based on the IEEE 802.11 standard, 4G (e.g., LTE), or 5G (e.g., NR), just to name a few options.

EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a serving gateway 166, a Multimedia Broadcast Multicast Service (MBMS) gateway 168, a broadcast multicast service center (BM-SC) 170, and a Packet Data Network (PDN) gateway 172.MME 162 may communicate with a Home Subscriber Server (HSS) 174. The MME 162 is a control node that handles signaling between the UE 104 and the EPC 160. Generally, MME 162 provides bearer and connection management.

In general, user Internet Protocol (IP) packets are communicated through a serving gateway 166, which itself is connected to a PDN gateway 172. The PDN gateway 172 provides UE IP address allocation as well as other functions. The PDN gateway 172 and BM-SC 170 are connected to IP services 176, which may include, for example, the internet, intranets, IP Multimedia Subsystems (IMS), PS streaming services, and/or other IP services.

The BM-SC 170 may provide functionality for MBMS user service configuration and delivery. The BM-SC 170 may be used as an entry point for content provider MBMS transmissions, may be used to authorize and initiate MBMS bearer services within a Public Land Mobile Network (PLMN), and may be used to schedule MBMS transmissions. The MBMS gateway 168 may be used to distribute MBMS traffic to base stations 102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service and may be responsible for session management (start/stop) and for collecting eMBMS related charging information.

The 5gc 190 may include an access and mobility management function (AMF) 192, other AMFs 193, a Session Management Function (SMF) 194, and a User Plane Function (UPF) 195. The AMF 192 may communicate with a Unified Data Management (UDM) 196.

The AMF 192 is typically a control node that handles signaling between the UE 104 and the 5gc 190. In general, AMF 192 provides QoS flows and session management.

All user Internet Protocol (IP) packets are delivered through the UPF 195, which connects to the IP service 197 and provides IP address assignment for the UE as well as other functions for the 5gc 190. The IP services 197 may include, for example, the internet, an intranet, an IP Multimedia Subsystem (IMS), PS streaming media services, and/or other IP services.

Returning to fig. 2, various example components of BS102 and UE 104 (e.g., wireless communication network 100 of fig. 1) that may be used to implement aspects of the present disclosure are depicted.

At BS102, transmit processor 220 may receive data from data source 212 and control information from controller/processor 240. The control information may be for a Physical Broadcast Channel (PBCH), a Physical Control Format Indicator Channel (PCFICH), a physical hybrid ARQ indicator channel (PHICH), a Physical Downlink Control Channel (PDCCH), a group common PDCCH (GC PDCCH), and others. In some examples, the data may be for a Physical Downlink Shared Channel (PDSCH).

A Medium Access Control (MAC) -control element (MAC-CE) is a MAC layer communication structure that may be used for control command exchange between wireless nodes. The MAC-CE may be carried in a shared channel, such as a Physical Downlink Shared Channel (PDSCH), a Physical Uplink Shared Channel (PUSCH), or a physical side link shared channel (PSSCH).

Processor 220 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmission processor 220 may also generate reference symbols, such as for a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a PBCH demodulation reference signal (DMRS), and a channel state information reference signal (CSI-RS).

A Transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to Modulators (MODs) in the transceivers 232a-232 t. Each modulator in transceivers 232a-232t may process a respective output symbol stream (e.g., for OFDM) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators in transceivers 232a-232t may be transmitted through antennas 234a-234t, respectively.

At the UE 104, antennas 252a-252r may receive the downlink signals from the BS102 and may provide the received signals to a demodulator (DEMOD) in transceivers 254a-254r, respectively. Each demodulator in transceivers 254a-254r may condition (e.g., filter, amplify, downconvert, and digitize) a corresponding received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM) to obtain received symbols.

MIMO detector 256 may obtain received symbols from all demodulators in transceivers 254a-254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data to the UE 104 to a data sink 260, and provide decoded control information to a controller/processor 280.

On the uplink, at the UE 104, a transmit processor 264 may receive and process data from a data source 262 (e.g., for a Physical Uplink Shared Channel (PUSCH)) and control information from a controller/processor 280 (e.g., for a Physical Uplink Control Channel (PUCCH)). The transmission processor 264 may also generate reference symbols for a reference signal, e.g., a Sounding Reference Signal (SRS). The symbols from transmit processor 264 may be pre-decoded, if applicable, by a TX MIMO processor 266, further processed by modulators in transceivers 254a-254r (e.g., for SC-FDM), and transmitted to BS102.

At BS102, uplink signals from UE 104 may be received by antennas 234a-234t, processed by demodulators in transceivers 232a-232t, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by UE 104. The receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to a controller/processor 240.

Memory 242 and memory 282 may store data and program codes for BS102 and UE 104, respectively.

The scheduler 244 may schedule UEs for data transmission on the downlink and/or uplink.

The 5G may utilize Orthogonal Frequency Division Multiplexing (OFDM) with Cyclic Prefix (CP) on uplink and downlink. 5G may also support half duplex operation using Time Division Duplex (TDD). OFDM and single carrier frequency division multiplexing (SC-FDM) divide the system bandwidth into multiple orthogonal subcarriers, which are also commonly referred to as tones and bins. Each subcarrier may be modulated with data. The modulation symbols may be transmitted in the frequency domain using OFDM and in the time domain using SC-FDM. The interval between adjacent subcarriers may be fixed and the total number of subcarriers may depend on the system bandwidth. In some examples, the minimum resource allocation, referred to as a Resource Block (RB), may be 12 consecutive subcarriers. The system bandwidth may also be divided into a plurality of sub-bands. For example, a subband may cover multiple RBs. NR may support a 15KHz base subcarrier spacing (SCS) and other SCSs may be defined relative to the base SCS (e.g., 30KHz, 60KHz, 120KHz, 240KHz, and others).

As described above, fig. 3A-3D depict various example aspects of a data structure for a wireless communication network, such as wireless communication network 100 of fig. 1.

In aspects, the 5G frame structure may be Frequency Division Duplex (FDD), where for a particular set of subcarriers (carrier system bandwidth), the subframes within the set of subcarriers are dedicated to DL or UL. The 5G frame structure may also be Time Division Duplex (TDD), where for a particular set of subcarriers (carrier system bandwidth), the subframes within the set of subcarriers are dedicated to both DL and UL. In the example provided by fig. 3A and 3C, the 5G frame structure is assumed to be TDD, with subframe 4 configured with slot format 28 (mostly DL) and subframe 3 configured with slot format 34 (mostly UL), where D is DL, U is UL, and X is flexible for use between DL/UL. Although subframes 3,4 are shown with slot formats 34, 28, respectively, any particular subframe may be configured with any of the various available slot formats 0-61. The slot formats 0, 1 are DL, UL, respectively. Other slot formats 2-61 include a mix of DL, UL and flexible symbols. The UE is configured with a slot format (dynamically configured by DL Control Information (DCI) or semi-statically/statically configured by Radio Resource Control (RRC) signaling) by a received Slot Format Indicator (SFI). Note that the following description also applies to a 5G frame structure that is TDD.

Other wireless communication technologies may have different frame structures and/or different channels. A frame (10 ms) may be divided into 10 equally sized subframes (1 ms). Each subframe may include one or more slots. The subframe may also include a micro slot, which may include 7, 4, or 2 symbols. In some examples, each slot may include 7 or 14 symbols, depending on the slot configuration.

For example, for slot configuration 0, each slot may include 14 symbols, and for slot configuration 1, each slot may include 7 symbols. The symbol on DL may be a Cyclic Prefix (CP) OFDM (CP-OFDM) symbol. The symbols on the UL may be CP-OFDM symbols (for high throughput scenarios) or Discrete Fourier Transform (DFT) -spread OFDM (DFT-s-OFDM) symbols (also known as single carrier frequency division multiple access (SC-FDMA) symbols) (for power limited scenarios; limited to single stream transmission).

The number of slots within a subframe is based on the slot configuration and the parameter set. For slot configuration 0, different parameter sets (μ) 0 through 5 allow 1, 2, 4, 8, 16, and 32 slots, respectively, per subframe. For slot configuration 1, different parameter sets 0 to 2 allow 2, 4 and 8 slots, respectively, per subframe. Thus, for slot configuration 0 and parameter set μ, there are 14 symbols/slot and 2 μ slots/subframe. The subcarrier spacing and symbol length/duration are functions of the parameter set. The subcarrier spacing may be equal to 2 ^μ x 15kHz, where μ is the parameter set 0 to 5. Thus, parameter set μ=0 has a subcarrier spacing of 15kHz, while parameter set μ=5 has a subcarrier spacing of 480 kHz. The symbol length/duration is inversely related to the subcarrier spacing. Fig. 3A to 3D provide examples of a slot configuration 0 having 14 symbols per slot and a parameter set μ=2 having 4 slots per subframe. The slot duration is 0.25ms, the subcarrier spacing is 60kHz, and the symbol duration is approximately 16.67 mus.

The resource grid may be used to represent a frame structure. Each slot includes Resource Blocks (RBs) (also referred to as Physical RBs (PRBs)) that extend for 12 consecutive subcarriers. The resource grid is divided into a plurality of Resource Elements (REs). The number of bits carried by each RE depends on the modulation scheme.

As shown in fig. 3A, some REs carry reference (pilot) signals (RSs) for UEs (e.g., UE 104 of fig. 1 and 2). The RSs may include demodulation RSs (DM-RSs) (denoted Rx for one particular configuration, where 100x is a port number, but other DM-RS configurations are also possible) and channel state information reference signals (CSI-RSs) for channel estimation at the UE. The RSs may also include beam measurement RSs (BRSs), beam Refinement RSs (BRRSs), and phase tracking RSs (PT-RSs).

Fig. 3B shows an example of various DL channels within a subframe of a frame. A Physical Downlink Control Channel (PDCCH) carries DCI within one or more Control Channel Elements (CCEs), each CCE including nine RE groups (REGs), each REG including four consecutive REs in an OFDM symbol.

The Primary Synchronization Signal (PSS) may be within symbol 2 of a particular subframe of a frame. PSS is used by the UE (e.g., 104 of fig. 1 and 2) to determine subframe/symbol timing and physical layer identity.

The Secondary Synchronization Signal (SSS) may be within symbol 4 of a particular subframe of a frame. SSS is used by the UE to determine the physical layer cell identification group number and radio frame timing.

Based on the physical layer identity and the physical layer cell identity group number, the UE may determine a Physical Cell Identifier (PCI). Based on the PCI, the UE can determine the location of the aforementioned DM-RS. A Physical Broadcast Channel (PBCH) carrying a Master Information Block (MIB) may be logically grouped with PSS and SSS to form a Synchronization Signal (SS)/PBCH block. The MIB provides the number of RBs in the system bandwidth and a System Frame Number (SFN). The Physical Downlink Shared Channel (PDSCH) carries user data, broadcast system information such as System Information Blocks (SIBs) that are not transmitted over the PBCH, and paging messages.

As shown in fig. 3C, some REs carry DM-RS for channel estimation at the base station (indicated as R for one particular configuration, but other DM-RS configurations are possible). The UE may transmit DM-RS of a Physical Uplink Control Channel (PUCCH) and DM-RS of a Physical Uplink Shared Channel (PUSCH). The PUSCH DM-RS may be transmitted in the previous or the previous two symbols of the PUSCH. The PUCCH DM-RS may be transmitted in different configurations according to whether the short PUCCH or the long PUCCH is transmitted and according to a specific PUCCH format used. The UE may transmit a Sounding Reference Signal (SRS). The SRS may be transmitted in the last symbol of the subframe. The SRS may have a comb structure, and the UE may transmit the SRS on one of the comb teeth. The SRS may be used by the base station for channel quality estimation to enable frequency dependent scheduling of the UL.

Fig. 3D shows examples of various UL channels within a subframe of a frame. The PUCCH may be located at a position as indicated in one configuration. The PUCCH carries Uplink Control Information (UCI) such as a scheduling request, a Channel Quality Indicator (CQI), a Precoding Matrix Indicator (PMI), a Rank Indicator (RI), and HARQ ACK/NACK feedback. PUSCH carries data and may additionally be used to carry Buffer Status Reports (BSR), power Headroom Reports (PHR), and/or UCI.

Additional considerations

The foregoing description provides an example of a beam refinement procedure in a communication system. The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. The examples discussed herein are not limited in scope, applicability, or aspect to the description set forth in the claims. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. For example, changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, replace, or add various procedures or components as appropriate. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method practiced using any number of the aspects set forth herein. In addition, the scope of the present disclosure is intended to cover such an apparatus or method that is practiced using other structure, functionality, or both in addition to or instead of the aspects of the present disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of the claims.

The techniques described herein may be used for various wireless communication techniques such as 5G (e.g., 5 GNR), 3GPP Long Term Evolution (LTE), advanced LTE (LTE-a), code Division Multiple Access (CDMA), time Division Multiple Access (TDMA), frequency Division Multiple Access (FDMA), orthogonal Frequency Division Multiple Access (OFDMA), single carrier frequency division multiple access (SC-FDMA), time division-synchronous code division multiple access (TD-SCDMA), and other networks. The terms "network" and "system" are often used interchangeably. CDMA networks may implement technologies such as Universal Terrestrial Radio Access (UTRA), CDMA2000, and other radios. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95, and IS-856 standards. TDMA networks may implement radio technologies such as global system for mobile communications (GSM). An OFDMA network may implement radio technologies such as NR (e.g., 5G RA), evolved UTRA (E-UTRA), ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, flash-OFDMA, etc. UTRA and E-UTRA are parts of Universal Mobile Telecommunications System (UMTS). LTE and LTE-a are versions of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-a and GSM are described in documents from an organization named "third generation partnership project" (3 GPP). Cdma2000 and UMB are described in documents from an organization named "third generation partnership project 2" (3 GPP 2). NR is an emerging wireless communication technology being developed.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general purpose processor, a DSP, an ASIC, a Field Programmable Gate Array (FPGA) or other Programmable Logic Device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, a system-on-a-chip (SoC), or any other such configuration.

If implemented in hardware, an example hardware configuration may include a processing system in a wireless node. The processing system may be implemented using a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including processors, machine-readable media, and bus interfaces. The bus interface may be used to connect a network adapter or the like to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of user equipment (see fig. 1), user interfaces (e.g., keypad, display, mouse, joystick, touch screen, biometric sensor, proximity sensor, light emitting element, and others) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripheral equipment, voltage regulators, power management circuits, and the like, which are well known in the art and therefore will not be described further. A processor may be implemented with one or more general-purpose processors and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality of the processing system depending on the particular application and the overall design constraints imposed on the overall system.

If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Software should be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general-purpose processing, including the execution of software modules stored on a machine-readable storage medium. A computer readable storage medium may be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable medium may comprise a transmission line, a carrier wave modulated by data, and/or a computer-readable storage medium having stored thereon instructions separate from the wireless node, all of which may be accessed by a processor through a bus interface. Alternatively or additionally, the machine-readable medium or any portion thereof may be integrated into the processor, such as in the case of having a cache and/or general purpose register file. By way of example, examples of machine-readable storage media may include RAM (random access memory), flash memory, ROM (read only memory), PROM (programmable read only memory), EPROM (erasable programmable read only memory), EEPROM (electrically erasable programmable read only memory), registers, a magnetic disk, an optical disk, a hard disk drive, or any other suitable storage medium, or any combination thereof. The machine-readable medium may be embodied in a computer program product.

A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer readable medium may include a plurality of software modules. The software modules include instructions that, when executed by an apparatus, such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a reception module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, when a trigger event occurs, the software module may be loaded from the hard disk drive into RAM. During execution of the software module, the processor may load some of the instructions into the cache to increase access speed. One or more cache lines may then be loaded into a general purpose register file for execution by a processor. When reference is made below to the functionality of a software module, it will be understood that such functionality is implemented by the processor when executing instructions from the software module.

As used herein, a phrase referring to "at least one item in a list of items" refers to any combination of these items (which includes a single member). For example, at least one of "a, b, or c" is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination of multiple identical elements (e.g., a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b-c, c-c, and c-c-c, or any other ordering of a, b, and c).

As used herein, the term "determining" encompasses a wide variety of actions. For example, "determining" may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, "determining" may include receiving (e.g., receiving information), accessing (e.g., accessing data in memory), and so forth. Further, "determining" may include parsing, selecting, choosing, establishing, and so forth.

The methods disclosed herein comprise one or more steps or actions for achieving the method. Method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. Furthermore, the various operations of the methods described above may be performed by any suitable means capable of performing the corresponding functions. The component may include various hardware and/or software components and/or modules including, but not limited to, a circuit, an Application Specific Integrated Circuit (ASIC), or a processor. Generally, where there are operations shown in the figures, those operations may have corresponding, numbered-like correspondence with component plus function assemblies.

The following claims are not intended to be limited to the aspects shown herein but are to be accorded the full scope consistent with the language of the claims. Within the claims, reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more. The term "some" means one or more unless specifically stated otherwise. No claim element should be construed in accordance with the specification of 35u.s.c. ≡112 (f) unless the phrase "means for … …" is used to express the element explicitly or, in the case of method claims, the phrase "step for … …" is used to express the element. All structural and functional equivalents to the elements of the aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Furthermore, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.

Claims

1. A method for wireless communication by a first device, comprising:

Participating in a first training process to obtain a set of channel estimates corresponding to different paths between a second device and the first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components;

using the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS component based on at least one target; and

Communicating with the second device using the RIS component configured according to the combination vector.

2. The method according to claim 1, wherein:

The first device comprises a User Equipment (UE) and the second device comprises a base station;

the first device comprises a base station and the second device comprises a UE; or alternatively

The first device includes a UE and the second device includes a UE.

3. The method of claim 1, wherein the at least one objective is to combine signals reflected by the RIS component to enhance a received signal at the first device.

4. A method according to claim 3, wherein the combined vector is obtained using singular value decomposition to select the eigenvector corresponding to the highest eigenvalue.

5. The method of claim 1, wherein the at least one objective is to cancel a signal reflected by the RIS component to zero interference at one or more other devices.

6. The method of claim 5, wherein the combined vector is obtained using singular value decomposition to select eigenvectors corresponding to zero eigenvalues.

7. The method of claim 1, wherein the combined vector comprises a set of common coefficients, wherein common coefficients from the set are used at each RIS component.

8. The method of claim 7, wherein the RIS component comprises one or more individual RIS and one or more RIS clusters.

9. The method of claim 8, wherein the set of common coefficients comprises common coefficients used across all elements of different RIS in a RIS cluster.

10. The method of claim 1, wherein participating in a first training process comprises:

performing a first channel measurement based on a first reference signal received when all of the RIS components are disabled; and

One or more other channel measurements are performed based on one or more reference signals received when only one RIS component is enabled.

11. The method of claim 10, wherein the first device calculates the combining vector based on a first channel measurement and other channel measurements.

12. The method of claim 1, wherein the first device calculates the combined vector, quantizes a value of the combined vector, and transmits the quantized value to at least one of a RIS controller or the second device.

13. The method according to claim 1, wherein:

the combining vector is based on a Precoding Matrix Indicator (PMI) codebook; and

The codebook is configured by the first device or the codebook is configured based at least in part on feedback recommendations from the second device.

14. The method of claim 1, wherein the RIS component comprises a portion of the RIS surface segmented into sub-RIS.

15. The method of claim 1, further comprising: signaling is received indicating the at least one target on which the combining vector is based.

16. The method of claim 15, wherein the signaling comprises at least one of Radio Resource Control (RRC), medium Access Control (MAC) Control Element (CE), or Downlink Control Information (DCI) signaling a Physical Downlink Shared Channel (PDSCH), side chain control information (SCI), or physical side chain shared channel (PSSCH).

17. A method for wireless communication by a second device, comprising:

Configuring a first device to participate in a first training process to obtain a set of channel estimates corresponding to different paths between a second device and the first device involving reflections from different Reconfigurable Intelligent Surface (RIS) components, and using the set of channel estimates to participate in a second training process to obtain a combined vector of coefficients for configuring the RIS components based on at least one target;

engaging in the first training process and the second training process with the first device; and

Communicating with the first device using the RIS component configured according to the combination vector.

18. The method of claim 17, wherein the participating comprises:

receiving information about the combined vector of coefficients from the first device; and

Communicate with one or more RIS controllers to configure the RIS components according to the information.

19. The method of claim 17, wherein the participating comprises requiring the first device to calculate the combining vector.

20. The method of claim 17, wherein the second device configures a plurality of Precoding Matrix Indicators (PMIs) and receives an indication of one of the plurality of PMIs from the first device.

21. An apparatus for wireless communication by a first device, comprising:

A memory; and

At least one processor coupled with the memory, wherein the memory includes instructions executable by the at least one processor to cause the first device to

22. The apparatus of claim 21, wherein:

The first device includes a UE and the second device includes a UE.

23. The apparatus of claim 21, wherein the at least one objective is to combine signals reflected by the RIS component to enhance received signals at the first device.

24. The device of claim 23, wherein the combined vector is obtained using singular value decomposition to select a eigenvector corresponding to a highest eigenvalue.

25. The apparatus of claim 21, wherein the at least one objective is to cancel a signal reflected by the RIS component to zero interference at one or more other devices.

26. The device of claim 25, wherein the combined vector is obtained using singular value decomposition to select eigenvectors corresponding to zero eigenvalues.

27. The device of claim 21, wherein the combined vector comprises a set of common coefficients, wherein common coefficients from the set are used at each RIS component.

28. The apparatus of claim 21, wherein the at least one processor and the memory are configured to:

29. The apparatus of claim 21, wherein the at least one processor and the memory are further configured to receive signaling indicating the at least one target on which the combined vector is based.

30. An apparatus for wireless communication by a second device, comprising:

A memory; and

At least one processor coupled with the memory, wherein the memory includes instructions executable by the at least one processor to cause the second device to